Cheyladd

I am having an odd cooling issue with my LS3. Motor is a brand new crate motor. At idle and on the road, if my rpm's are low the motor will build heat and run up to about 220 and beyond if I am not careful. If I run the rpm's up to over 3k, it cools right back down. It has the gmpp cts-v style accessory kit so as far as getting something in backwards or not being the right "size," it seems that shouldn't be the case. Idling, around town driving, or freeway driving doesn't make any difference. rpm's seem to be the only thing that will cool it down.

The cooling system is a 4 core radiator, surge tank and front 2 steam ports routed to the surge tank.

Any thoughts? The obvious seems that the water pump isn't circulating fast enough at low rpm's but that doesn't make sense given I am using the recommended gmpp combination of parts.

joyridin'

iTrader: (1)

What are you using to determine the temperature? If some sort of aftermarket gauge, where do you have it plumbed in at? What computer system are you using? GMPP also?

Cheyladd

Autometer aftermarket gauge to determine temp plumbed off the top back of the intake. Computer kicks fan on at 207 and my gauge reads 200 when it kicks on so it is close but not exact.

The computer was provided by Speartech. I originally used gmpp everything but had lots of issues with the wire harness. Dumped all of that and am now running a Speartech harness and computer.

Gray86hatch

iTrader: (83)

The intake has no water in it. Must get temp from the cyl head.

Tim

Cheyladd

Sorry. You are correct. I was looking at my oil pressure sender. Coolant sender is on the passenger side cyl head just behind the rear of the exhaust manifold.

dw456post

Do you have a used water pump? What is your thermostat temp rating?

Cheyladd

The motor and all accessories are brand new with the install including the water pump. Thermostat is the one that came in it. 190.

joyridin'

iTrader: (1)

Do you have the correct sending unit? The autometer version I have reads head temperature, not water temp. Not sure what the difference is as it screws into the rear port like yours, but the temp jumps like yours also. I hooked up HPTuners and the unit in the drivers side head as read by the computer does not jump around like the Autometer version. Fan kicks on at 210 and off ar 200 if I recall.

Cheyladd

I definitely have the correct sender. It took me a while to sort out where I was going to put it and was careful as I ordered it since I was matching the gauge I already had.

I also know my temps are actually changing because when it gets higher it will release the cap on my surge tank.

handyandy496

iTrader: (9)

I know this sounds weird but I read a thread stating that there is a difference of water temp between the left head and the right head temp at the temp sensor holes. The LH being the correct spot for the sender. If I remember correctly it was about 20* hotter at the RH near the fire wall I think.
Someone correct me if I'm wrong.

SydwayZ

Maybe the water pump. Was it used or new with the crate?

joyridin'

iTrader: (1)

That is what I see with my Autometer gauge plumbed into the rear right. I did not have a problem with the surge tank though, but that may be just the way I have it plumbed. When I hook the computer up to the OBD port and read the ECU temp, it is showing the correct temps and the fan kicks on/off like normal.

joyridin'

iTrader: (1)

What is your fan doing? Is it cycling or running continuously?

Cheyladd

That might explain the difference between when my fan kicks on and what my gauge is reading. The sensor that sends a reading to the ecm is on the drivers side front. The sensor for my gauge is on the passenger side rear.

Cheyladd

I can only get the fan to kick off when I rev the engine to bring the temps down. Otherwise it runs all the time.

Interestingly I wired in a switch on my fan to turn it off on the freeway to see if it running all the time on the freeway was necessary. It didn't change the temp at all having it off on the freeway but it doesn't drop enough to automatically turn the fan off unless I run in 4th gear and get the rpms up.

Project GatTagO

iTrader: (7)

Sounds like you have air in the system. What vehicle is this installed into?

I've had good luck with backfilling the system through the vent hose. Attach a 2 foot hose to the crossover nipple, use a small funnel. It's a slow process but works well in completely filling the block and purging any air that might be present.

Andrew

Cheyladd

It is installed in a 1966 International Travelette 4x4. I will try your idea and see if it helps. Thanks.

Cheyladd

Efi69cam

That is probably the coolest ls recipient I've seen.

Is the surge tank plumbed with a tee off the water pump like the LS trucks e.g. 2004ish silverado?

Cheyladd

Thank you. I agree but am biased.

Yes, the surge tank is plumbed off the water pump with a T and the steam tubes are also plumbed to the surge tank like on the trucks.